The impact of anthropogenic N deposition: The evidence from fire chronosequences, and from experimental nitrogen addition studies (Gundale et al. 2011) suggest that N fixation in the feather moss layer is down-regulated under conditions of enhanced nitrogen availability. We extend this work to look at the potential effects of anthropogenic N deposition on boreal N fixation. Under increasing N deposition, do boreal forest mosses retain to the capacity to build N capital? We also have limited understanding of the fate of N fixed by the cyanobacteria. We expect that much of it is conserved in the moss layer, with most of the fixed N liberated only occasionally during disturbance events such as fire. How is N fixed by feathermoss-cyanobacterial communities cycled and taken up by higher plants?

Carbon and nitrogen dynamics of natural and disturbed ecosystems: Soil and understorey CO2, CH4, and N2O greenhouse gas (GHG) fluxes are directly influenced by stand age and associated N fertility conditions in boreal forests (Ball et al.2007). As yet, there is no direct evidence of the influence of N fixation on green house gas emissions in boreal forests, but soil NO3- accumulation and increased net nitrification after fire has been observed for up to 30 years (DeLuca et al. 2002, DeLuca et al. 2006).

Fire as a driver of ecosystem processes in forest ecosystems:Recurrent, low to moderate severity fires in temperate and part of the soil O horizon. Depending on severity, a portion of the total ‘ecosystem N capital’ contained within plant and soil material is lost to combustion. After fire, there is an associated increase in inorganic N availability, with the amount of N in throughfall elevated after fire, then decreasing as succession progresses. Organic N resources lost through combustion during severe wildfire events are eventually recovered through feathermoss-cyanobacterial N-fixation.